Hammer for impact crushing or grinding apparatus



April 29, 1941. A. KING 2,240,404

HAMMER FOR IMPACT CRUSHING 0R GRINDING APPARATUS Filed Jan. 16, 1340 3 Sheets-Sheet 1 W2 a/ 1110mm (WA M 2s A lfomey April 29, 1941. A m 2,240,404

HAMMER FOR IMPACT CRUSH ING 0R GRINDING APPARATUS Filed Jan. 1 6, 1940 a Sheets-Sheet 2 A. KING 2,240,404

HAMMER FOR IMPACT CRUSHING 0R GRINDING APPARATUS April 29, 1941.

Filed Jan. 16, 1940 3 Sheets-Sheet 3 fzzverziar X Llilarne wigs m u/WICCN I l I l-Ill. II. III

Patented Apr. 29, 1941 ()FFICE HAMMER FOR IMPACT CRUS'HING R GRINDING APPARATUS I AlfredKing, Hackney, Matlock, England Application January 16, 1940, "Serial No. 314,171 In Great Britain December 1, 1938 2 Claims.

The present invention relates toimprovements in hammer or beater mills of the type in which one or more hammers or heaters are loosely mounted about pivots rotatable about a centre so that the said hammers or heaters swing outwardly about the pivots by reason of their inertia on materials to be crushed or ground.

In devices of this type it has been usual to form the hammer head with a number of projections, its boss being bored out and provided with semi-cylindrical recesses disposed in a number of positions similar to the bosses of the hammer head, in any one recess of which a single supporting cylindrical pin on the hammer arm is adapted to engage.

A mill is also known in which hammer heads have been provided with a number of recesses similar to the number of external projections, the head being freely supported about two supporting pins or points only one of which at any one time however, could be accommodated within a recess.

It has been found that with hammer heads of this type the effective life is short in that only a limited area of the head is in use or capable of use even after sharpening or grinding.

According to the present invention a hammer head for a grinding or crushing mill of this type is formed as an annulus provided with a number of projections on its outer periphery whilst the interior surface of the annulus is provided with an equal number of separate evenly spaced sockets two of which at any one time are adapted to be engaged by a pair of spaced supports fixed on the arm, the maximum width of which supports is less than the least internal diameter of the annulus.

By this means the hammer head is held against movement about its support on the arm except at such times when it is positively dislodged therefrom, whereupon under the action of centrifugal force it immediately can become engaged upon another pair of sockets.

The sockets may either be concave or convex; they may be part cylindrical or may be straight sided.

The invention is more particularly described with reference to the accompanying drawings, in which:

Figure 1 shows a hammer head in one form of construction,

Figure 2 shows a modified form of hammer.

Figures 3, 4 and 5 are similar views of further forms of construction.

Figure -6 is a detail view of a modified form of device.

Figure '7 is a view of a further modification.

The hammer head comprises an annulus I having on its outer periphery projections 2, of dog tooth section, that is to say, having the leading side 3 either radial to the virtual centre of the annulus or as shown in Figure 1, tangential to a circle of smaller diameter than the outer periphery of the annular'hammer head whilst the other or trailing surface 4 lies at an acute angle to the surface 3.

On the inner periphery of the annulus l, a plurality of concave sockets 5 are provided equal in number and angular disposition to the teeth 2 which sockets cooperate with a pair of bearing pins 6 disposed with their centres spaced apart and spaced from the virtual centre 1 of the annulus, and which pins are carried on the hammer arms 8 freely rotatable about a crank pin 9 on the rotatable disc of the machine.

It will consequently be seen that as the hammer arm moves forward in the direction of the arrow A, the leading surface 3 of the dog tooth projections 2 will impact against material crushing this, the particles ground passing through a screen II] in normal manner.

From time to time the annulus I due to impact on a lump of material to be crushed will become dislocated from its supporting pins 6, l and by centrifugal force about the centre of the rotating crank discs, or about the centre of the pin 9, and will take up a fresh position.

The advantage of this construction is that the whole of the periphery becomes useful as a grinding or impact surface so that the useful life of the hammer or beater is very considerably extended. In the modified form of the hammer head as shown in Figure 2 the trailing edge of the teeth is backed off as shown at H giving a greater strength of tooth or projection.

To assist in the grinding of the teeth when worn one or more fine grooves such as I2 may be provided in the side surface of the annular hammer head concentric with the centre of these to assist in the setting up of the head during the grinding operation.

It is obvious that instead of providing a pair of pins as shown in Figure 1, a bridge such as l 3, Figure 2 may be provided having convex ends engaging on the concave sockets in the annulus.

Further, instead of providing concave sockets in the annulus engaging convex surfaces, or pins or a bridge such as l3, the inner periphery of the annulus may be provided with convex sockets or seen from Figure 4. Further the sides of the sockets may be straight as shown in Figure 5. In

each case however, it is important that the maximum width (a) of the supports formed'by the pins or bridge is less than the least diameter (b) of the annulus to allow freedom of displacement and relodging of the hammer head.

As shown in Figure 6, a spring it of springy strip metal can be provided having a convexl op I! to engage a recess in the hammer head and I one or a pair of concave loops l8, I9 to engage the sides of the fixed pin 20 or of the pins 26 and 2| respectively. It will be seen that with this device a kind of ratchet effect is obtained, further ensuring displacement of the hammer head 22 about the supporting pins 29, 2|.

The end 23 of the spring clip I6 is preferably rounded as shown so that should it be accidentally dislodged from the pins 20, 2|, it will automatically snap back into position a As shown in Figure 7 the end 24 of the spring clip 25'itself may form one support, whilst a single rigid pin 26 forms a second support for the hammer head 29. The spring clip 25 may be extended to engage a number of sockets as shown in dotted lines at 28.

I declare that What I claim is:

1. A grinding mill including a rotatable arm, a hammer head loose thereon in the form of an annulus having a number of projections on its outer periphery, whilst the interior surface of the annulus is provided with an equal number of separate evenly spaced sockets, and a pair of spaced supports fixed on the arm, two of which at any 7 one time engage said sockets, the maximum width of which supports is less than the least internal diameter of the annulus, and a spring clip elastically engaging said spaced supports and a socket on the annulus. 

